The present invention relates to a package for a semiconductor used in electronic equipment and a method for forming the semiconductor package.
A semiconductor is an essential component in forming circuits of electronic equipment and, various forms for mounting semiconductors have been developed and practiced lately. A form of a package as shown in FIG. 12 has been employed to facilitate handling and mounting semiconductors in the prior art.
An example of the aforementioned prior art will be described with reference to the drawing.
FIG. 12 shows a sectional view of a form of a conventional semiconductor package.
A semiconductor 1 has an upper first electrode 2 (upper a electrode) and an upper second electrode 3 (upper b electrode) set to one face, and a lower electrode 5 set to an opposite end face in its entirety. A circuit board 7 has predetermined circuit patterns formed on both faces which are joined by a through hole conductor (not shown), thereby forming a single circuit by the two faces. In some cases, balls 8 essentially consisting of gold, silver, copper, or solder are joined, as connecting bodies for connecting the circuit board 7 to another electric circuit, or to a circuit pattern of another circuit board to facilitate connection of the circuit board 7 to the another electric circuit.
The semiconductor package is formed by joining the semiconductor 1 and the circuit board 7 to one another. First, the lower electrode 5 is joined by solder 6 to the circuit pattern of the circuit board 7. A conductive paste or gold may be used in place of the solder 6 for joining the lower electrode 5 to the circuit pattern.
Meanwhile, the upper first electrode 2 (upper a electrode) and the upper second electrode 3 (upper b electrode) are generally connected to the circuit pattern by wire bonding with use of a gold wire or aluminum wire 4.
In order to protect a circuit forming part primarily consisting of the semiconductor 1, the circuit board 7 at the face to which the semiconductor 1 is mounted is coated with use of an insulating resin 9 in a manner not to deform the joining gold wire or aluminum wire 4. The semiconductor package is formed in this manner with a protection effect and ease of use improved.
The insulating resin 9 is supplied by molding with use of a mold, pouring molten resin, heating and melting resin in the form of powder or particles after placing the resin on an upper face of the semiconductor 1, or by a similar manner, thereby coating the semiconductor entirely.
When the semiconductor is heated to a great extent in the above-described constitution, the circuit board is not sufficient to radiate heat. Even if the circuit board is formed of ceramic exhibiting good heat conductivity, and used to radiate heat to a heat radiating plate or the like, emphasis is put on forming the circuit pattern; that is, heat radiation is not taken into considerable consideration, whereby a radiation lose is easily generated. Also, even if the gold wire or aluminum wire is utilized to radiate heat, since the gold wire or aluminum wire used for wire bonding is limited in diameter, the wire should be used within a current capacity allowed for its diameter. A plurality of joints must be carried out for one electrode to cope with a large current as in a power source circuit. Although a distance between electrodes must be secured to ensure safety and reliability in accordance with a current increase, the distance is hard to secure in the case where the gold wire or aluminum wire is used because the wire is varied in shape at the time of wire bonding, deformed during subsequent processes, or the like.